Thermal conductivity where (w) denotes the water phase



See Dynamic or absolute viscosity



Liquid’s density defined as a liquid is its mass per unit volume



Soil mass density or particle density



Soil bulk density/average bulk density defined as for mostly powders and granules, the mass of many particles of the material divided by the total volume they occupy/the average density value of the control volume material



Water density defined as water is its mass per unit volume



Vapour-liquid Interfacial tension/Surface tension defined as the elastic tendency of a fluid surface which makes it acquire the least surface area possible



Total porosity also given as (α)



Average contact angle of the liquid-air interface



Effective porosity defined as the ratio of the volume of the voids of a soil or rock mass that can be drained by gravity to the total volume of the mass (ASTM D653-20), as given in [4]



Soil water potential/water potential defined as the quantification of the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure or matrix effects such as capillary action (which is caused by surface tension)

[M∙L−1∙T−2] or [L]


Matric pressure/matric potential at the wetting front defined as the difference between the applied air pressure and the water pressure. The pressure of the water in a pore of the medium relative to the pressure of the air United States Geological Survey—USGS, Glossary of Hydrologic Terms, as given in [50]

[M∙L−1∙T−2] or [L]


Angular relaxation frequency defined as the oscillation frequency